The present invention relates to a motor vehicle including an occupant restraint device with a control device which produces a triggering signal when a predefined hazard signal is generated as a function of signals of a safety sensor system.
In addition to “seat belts” which hold the vehicle occupant on the vehicle seat, occupant restraint devices, which are installed as standard in motor vehicles, also include “airbag systems” with an inflatable airbag. When not in use, the inflatable airbag is arranged folded up in an accommodating space, for example, under the windshield or in the footwell in the region of a dashboard/glove compartment covering, and emerges therefrom when inflated. The airbag is inflated temporarily by a sensor-controlled gas generator such that, in order to protect the occupant, a balloon-like impact cushion is formed which then deflates.
In order to counteract the forward displacement of a vehicle occupant as early as possible, restraints for vehicle occupants are generally triggered in a “pre-crash phase” when a situation critical in terms of the dynamics of the vehicle movement is identified. Generally, the seat belt is tensioned by an electronic belt tensioner in order to avoid undesirable movements of the occupant, since crash-active restraint systems, such as airbags or other positioning devices, such as extendable cushions, can deploy an optimum protective effect only in defined positions of the occupant.
The activation of occupant restraint devices of this type takes place in practice by evaluation of sensors of a safety sensor system which detects different travel state data and the states of control systems concerned with the dynamics of the vehicle movement. If a state which is critical in terms of the dynamics of the vehicle movement is identified in this case, the restraint devices for the vehicle occupants are activated in order to prevent an undesired movement of the occupant in the vehicle interior.
An example of a method for switching on such a safety system protecting the occupants in a motor vehicle is described in German patent document DE 38 03 426 A1, in which a signal output by at least one acceleration sensor is evaluated, a hazard signal is derived from the signal of the acceleration sensor, the hazard signal describing the anticipated forward displacement of the occupant, and the safety system is activated by the hazard signal if a predeterminable threshold value is exceeded.
However, it is problematic if a vehicle occupant is not secured by a seat belt, with, in particular, unsecured passengers being moved forward in an unchecked manner if an emergency braking situation unexpectedly occurs. If, as a consequence of such an undesired forward displacement of the occupant, a vehicle impact with airbag triggering or the extension of an impact cushion in the direction of the vehicle occupant occurs, the “Out-of-Position” situation of the vehicle occupant may have a negative effect causing the vehicle occupant to be exposed to a considerable action on the part of these occupant restraint devices due to being close to the airbag outlet opening or to the inoperative position of an extendible impact cushion. In this case, it should also be taken into consideration that the vehicle occupant who is in such a forwardly displaced “Out-of-Position” situation, does not remain static in front of the outlet opening of the corresponding occupant restraint device, but rather is subject to the inertia forces prevailing during the vehicle impact.
It is therefore the object of the present invention to provide a motor vehicle with an occupant restraint device, with the situation of a forwardly displaced vehicle occupant being better taken into consideration during the triggering of the occupant restraint device.
This and other objects and advantages are achieved according to the present invention by an occupant restraint device of a motor vehicle, the control device of which produces a triggering signal when a predefined hazard signal is generated as a function of signals of a safety sensor system. Accordingly, the occupant restraint device acts on a vehicle occupant by at least one impact cushion. According to the present invention, the control device generates the hazard signal at least as a function of vehicle acceleration signals and a belt state signal representing the activation or deactivation of a seat belt. The control device deactivates the occupant restraint device at least for a certain period of time and/or activates it at reduced power in the event of the seat belt being identified as having been deactivated and there being vehicle acceleration signals to which a critical forward displacement of the occupant is assigned if the seat belt is deactivated.
If the vehicle occupant is not secured and there is a braking action with a defined deceleration which may lead to an undesired forward displacement of the occupant, the occupant restraint device, which acts with an impact cushion on the vehicle occupant, is therefore deactivated temporarily or activated at reduced power in order to avoid too severe an action on the vehicle occupant. It is also possible to provide delayed activation at reduced force or in accordance with a predetermined, situation-adapted force profile. The triggering of the occupant restraint device is therefore adapted to the position of a vehicle occupant whose is not secured such that the latter is not unnecessarily severely and adversely affected by the occupant restraint device.
In order to take into consideration as precisely as possible the risk to which the vehicle occupant who is not secured is exposed when the occupant restraint device is triggered, it is advantageous if in order to generate the hazard signal, the control device evaluates the vehicle acceleration signals in terms of magnitude and their temporal profile, in particular in a pre-crash phase preceding a vehicle impact.
The evaluation of the vehicle deceleration profile in the period of time preceding the impact is a central element in deciding the temporal deactivation of the occupant restraint device or the activation thereof at reduced power with a reduced number of elements acting on the vehicle occupant.
Therefore, in a configuration of the occupant restraint device as an airbag module with a deployable airbag as impact cushion, the airbag can be deployed in at least two stages, if appropriate at differing power or dynamics, with the control device outputting a signal in order to trigger just one stage at a reduced power or with weaker triggering dynamics in the event of the seat belt being identified as having been deactivated and there being vehicle acceleration signals assigned to a critical forward displacement of the occupant. In the case of a known, two-stage airbag gas generator, this can mean that, in the event of the seat belt being identified as having been deactivated and there being vehicle acceleration signals assigned to a critical forward displacement of the occupant, the control device outputs a signal in order to trigger just the first stage, and the second stage or, if appropriate, even a further stage of the airbag is deactivated.
In an advantageous embodiment of the invention, it can be provided that the control device evaluates a deceleration magnitude, which is determined via a longitudinal acceleration sensor, and/or a deceleration magnitude, which is determined via a transverse acceleration sensor as a vehicle acceleration signal. In this case, a deceleration magnitude resulting from these deceleration magnitudes can also be determined and can be evaluated as vehicle acceleration sensor.
In addition or as an alternative thereto, the control device may evaluate a deceleration magnitude, which is determined via the vehicle speed, in the longitudinal direction of the vehicle as vehicle acceleration signal, with it being possible here to use the output signals of wheel rotational speed sensors as signals representing the vehicle speed.
The use of the signals of a longitudinal acceleration sensor and, if appropriate, of a transverse acceleration sensor and/or of wheel rotational speed sensors makes it possible to take the actual deceleration of the vehicle into consideration, and therefore, for example in the event of emergency braking with a low carriage way coefficient of friction and consequently only a small deceleration of the vehicle, no deactivation or a reduced triggering of the occupant restraint device takes place.
As a further input variable, the effective duration of the vehicle deceleration or of the particular deceleration magnitude may be measured, and the effective duration may be established via the longitudinal acceleration sensors, transverse acceleration sensors and wheel rotational speed sensors.
In addition to the configuration of the occupant restraint devices in an airbag system, it is furthermore possible to provide, as an occupant restraint device with an impact cushion, any desired movable impact bodies, the size, hardness, shape and position of which can be changed by an activation.
The definition of a critical forward displacement of the occupant is of great significance, and a forward displacement of the occupant may be considered critical when a forward displacement travel, which is calculated from the vehicle acceleration signals and its effective duration, is greater than a threshold of a forward displacement travel.
In this case, the threshold of the forward displacement travel can be defined in a simple manner as a function of the distance between a dashboard/glove compartment covering and a maximum rearward position of a vehicle seat or of the backrest thereof. The maximum forward displacement travel arises from the dimensional concept of the vehicle when the vehicle seat position is at the rearmost point, measured by way of the occupant upper body on the backrest until the first contact with the dashboard/glove compartment covering. This value can be determined from the constructional data of the vehicle and can be stored in the triggering algorithm of the occupant restraint device.
Since the maximum forward displacement travel is reduced depending on the longitudinal adjustment of the vehicle seat and inclination of the backrest, use can also be made, for example, of a signal from an electronic device for detecting the position of the vehicle seat, as is generally present in the case of a motorized seat adjustment device.
Whereas, in the case of a simple embodiment of the invention, the occupant can be depicted as a mass which is freely moveable in relation to the vehicle, it can furthermore also be provided to take a possible supporting of the occupant into consideration via a corresponding correction value or for morphological data of the vehicle occupant, which can be determined, for example, via a seat occupation device or via passenger compartment monitoring devices, and for further information about the occupant position, which information is available via devices of this type, to be output to the control device for activating the occupant restraint device.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.